1. Field of the Invention
The invention relates to a junction housing for use in undersea oil wells.
2. Description of the Prior Art
Close to each hydrocarbon well is arranged a Christmas tree which comprises necessary valves and other equipment for controlling the well and which is connected to necessary connecting pipes and cables extending from a platform or other control base, depending on the method of production. These connecting pipes comprise production pipes which convey the produced hydrocarbons to the platform, connecting pipes extending from the platform to the annulus defined between the casing pipes and the production pipes, and pipes for transmitting hydraulic power for controlling valves, release mechanisms and other equipment, and electrical cables for connecting each Christmas tree to the platform for the transmission of signals to the hydraulically controlled devices, and the transmission of signals from measuring and other instruments and from the hydrocarbon wells.
These pipes may be subject to internal wear, which in the case of the production pipe may be caused to a great extent by sand or the like entrained in the hydrocarbons. Furthermore, the pipes are subject to corrosion damage and, in addition, both the pipes and cables may be damaged by water, foreign objects and so on.
A hydrocarbon source may have 30 or more wells with their associated Christmas trees, pipes and cables, and since hydrocarbon wells may be in production for fifteen to twenty years or more, it will be understood that the pipes and cables have to be raised to the platform at intervals for inspection, and repair or replacement of defective components. Similarly, the Christmas trees have to be raised to the platform at intervals for the same purposes.
Proposals for the raising of equipment from subsea well installations for inspection, repair and replacement have been made previously. These proposals are mainly designed for water depths where divers or frogmen may aid in the raising operation, and are thus limited to certain depths. At greater depths assistance may be rendered by manned submarine vessels equipped with manipulating tools, but these are dependent on considerable freedom of movement in the area where connection and disconnection and raising take place, for which reason the wells have to be spaced a substantial distance from each other.
It is clear that with the drilling and production techniques in use today and in prospect, operating at steadily increasing water depths and with increasing numbers of well heads drawing from one and the same hydrocarbon source, it is necessary to develop the capacity for pulling up or raising the pipes and cables to the platform for inspection, and repair and replacement of defective parts.